The present invention is generally directed to an inertial reference system and, more specifically, to an inertial reference system for a spacecraft.
Today, many spacecraft attitude control systems (ACSs) utilize attitude control assemblies (ACAs), e.g., reaction wheel assemblies (RWAs) or control moment gyros (CMGs), to control the movement of an associated spacecraft. Typically, an inertial sensor has been incorporated within the spacecraft to allow the spacecraft ACS to determine the effect on the spacecraft when the speed of a wheel of an RWA has been changed or when a wheel of a CMG has been deviated from its main rotation axis. In a typical system, power for the inertial sensor, as well as other sensors (e.g., earth, sun and star sensors), and the wheels of an RWA or CMG have been provided via a central power bus, whose voltage may vary, e.g., between twenty and one-hundred volts. Due to the variation in bus voltage, each sensor and ACA has typically included its own internal power regulator, to provide an appropriate voltage level to the electronics of each assembly.
In addition, each sensor and wheel has normally included an interface, which may provide and receive information in a designated format (e.g., 1553 protocol). In a typical spacecraft, each sensor or wheel provides information to a central ACA processing system, such that the processing system can determine the telemetry of the spacecraft. In such spacecrafts, the inertial sensor has generally been designed with separate power and telemetry cables that couple the sensor to a primary power source (e.g., an array of solar panels) and the processing system. In this manner, the ACA processing system computes the spacecraft rates based on inputs provided directly from the inertial sensor.
It would be desirable for a spacecraft inertial reference system to include a secondary source of inertial reference information, which can provide a backup to inertial reference information provided by an inertial sensor. It would also be desirable for a spacecraft inertial reference system to include a source of inertial reference information that can be utilized in place of inertial reference information that has typically been provided by an inertial sensor, obviating the need for the inertial sensor, while at the same time reducing required cabling.